The right of priority under 35 U.S.C. xc2xa7119(a) is claimed based on German Patent Application No. 101 28 166.8, filed Jun. 9, 2001, the entire disclosure of which is hereby incorporated by reference.
The present invention relates to a method for adjusting a recirculating air fraction of inlet air delivered to a passenger compartment of a vehicle, and to an air-conditioning system for a vehicle.
In known heating and cooling/air-conditioning systems in vehicles, the flow of inlet air drawn in by a fan and then delivered to a passenger compartment can often be switched in continuous increments between outside air and the air present in the passenger compartment by an outside air/recirculating air adjustment device. This is done either by pressing a key on an operating control unit or by an automatic control as a function of the vehicle speed (dynamic pressure compensation) and/or as a function of a signal from a pollutant gas sensor. If a prolonged period of time is spent in the passenger compartment, there is a danger in the recirculating air mode, in which the inlet air is composed exclusively of air present in the passenger compartment, that an air mixture will form in the passenger compartment that is humid and deficient in oxygen, owing to the influence of the occupants. Such humidity may lead to fogging up of the vehicle windows or may cause the occupants to be uncomfortable. In the case of oxygen deficiency, it leads initially to an insidious deterioration in driving capability due to fatigue and lack of concentration. Except in regions having a tropical climate, therefore, the system is generally run with a relatively high outside air fraction. As a result, however, the heating and air-conditioning system has an increased power demand.
A known method of preventing an excessive concentration of pollutant gases and excessively high humidity in the passenger compartment air is to set the inlet air to a high outside air fraction, without measuring and taking account of the pollutant gas concentration and the humidity of the passenger compartment air for this purpose. Although heating/air-conditioning systems operating on this principle are inexpensive to manufacture, since they do not require any sensors for the pollutant gases and/or humidity in the passenger compartment air, they have a relatively high power consumption.
EP 0 825 044 A2 discloses a method for air mixture control in a heating/air-conditioning unit of a motor vehicle, in which the humidity of the passenger compartment air is measured by means of a sensor and the recirculating air fraction of the inlet air is adjusted as a function of this humidity. Also known is the use of gas sensors in order to determine the carbon dioxide content of the passenger compartment air. The disadvantage to these methods is the high cost of such sensors.
One object of the present invention is to provide an improved method for adjusting a recirculating air fraction of inlet air delivered to a passenger compartment of a vehicle, which permits a simple and hence inexpensive construction for a heating and cooling/air-conditioning system, which nevertheless provides performance advantages.
A further object of the invention is to provide an improved apparatus for adjusting a recirculating air fraction of inlet air delivered to a passenger compartment of a vehicle, as well as an improved heating and/or air-conditioning system and an improved vehicle embodying such an apparatus and system.
In accordance with one aspect of the present invention, there has been provided a method for adjusting a recirculating air fraction of inlet air delivered to a passenger compartment of a vehicle via an air-conditioning system, in order to avoid exceeding a predetermined limit value of at least one passenger compartment air parameter, comprising: determining at least one secondary parameter; from the at least one determined secondary parameter, indirectly determining the passenger compartment air parameter; and adjusting the recirculating air fraction as a function of the indirectly determined passenger compartment air parameter.
In accordance with another aspect of the invention, there is provided a device for adjusting a recirculating air fraction of inlet air delivered to a passenger compartment of a vehicle via an air-conditioning system, in order to avoid exceeding a predetermined limit value of at least one passenger compartment air parameter. The device comprises a system for determining at least one secondary parameter; a calculation device for indirectly determining the passenger compartment air parameter from the at least one determined secondary parameter; and a device for adjusting the recirculating air fraction as a function of the indirectly determined passenger compartment air parameter.
In accordance with yet another aspect of the invention, there has been provided a heating and/or air-conditioning system for a vehicle having a device for adjusting the recirculating air fraction of the inlet air delivered to a passenger compartment of the vehicle, wherein the device comprises a device of the type described above. A vehicle embodying such a heating and/or air-conditioning system is also provided according to the invention.
Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying figures of drawing.